\begin{tikzpicture}
    \tkzDefPoints{0/0/A,  4/0/B,  0.8/2.5/D, 3.2/2.5/C}
    \tkzInterLL(A,C)(B,D)  \tkzGetPoint{O}
    \tkzDrawPolygon(A,B,D,C)
    \tkzLabelPoints[above](C,D)
    \tkzLabelPoints[below](A,B)
    \tkzLabelPoints[right=0.5em](O)
\end{tikzpicture}

